Prevent site crashing due to markdown parsing errors

[liu-cong]

Currently if the site cannot parse the contents from source (e.g. llm-d) repos correctly, the page crashes.

Ideally we can add CI tests in those repos to make sure they don't break the site. We should also consider making the site more resilient and degrade gracefully (e.g., by showing raw markdown) if it cannot parse the original content.

cc @petecheslock